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Lens Cell Cleaning



 
 
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  #11  
Old February 12th 11, 05:33 PM posted to rec.photo.equipment.large-format
Jean-David Beyer
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Posts: 245
Default Lens Cell Cleaning

Cheesehead wrote:
Cheesehead wrote:
On Feb 9, 11:41 pm, "Richard Knoppow" wrote:

If its a standard Triplet the back cell will be a single
lens so there is no need to remove the glass. The front cell
will have two elements. Usually in larger lenses there is a
threaded back cap on the cell but it may have a retaining
ring on the front which is more common for smaller lenses.
If a back cap its easy to remove. The elements are clamped
between concentric edges in the cell so are automatically
centered.
If the cap is too tight for removal with simple finger
grip use one of those rubber jar grippers. It won't mar the
surface. If you grip too tightly it will clamp it and make
it even harder to remove.
I agree with the others about cleaning but if the lens
is oily the standard optical cleaner is pure acetone
followed by dry isopropyl alcohol. Window cleaner like
Windex may streak the lens if not followed by alcohol. The
newer butyl alcohol "streak-free" cleaners are better.
While ammonia is alkaline and strong alkalies can
dissolve some kinds of glass there is no real danger from
the very dilte ammonia in Windex and similar cleaners.
If you use acetone be careful of the edge paint, if any,
and of the paint on the cell because it will dissolve both.
I do not recommend cleaning inside elements when in a
shutter because there is too much danger of getting the
cleaning fluid into the shutter, take the cell out.

--
--
Richard Knoppow
Los Angeles, CA, USA


I'm not absolutely certain about the Geronar formula. It is reported
to be a Tessar.
That said, the rear should be a single piece of glass. But it is not.
If it is a cemented piece, then it is not a true Tessar and the
fogging may be in the cement.
That would be bad.
I've not found the formula out there to describe the lens.
In the mean time I've been searching for a replacement rear cell.



--
.~. Jean-David Beyer Registered Linux User 85642.
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On Feb 9, 11:41 pm, "Richard Knoppow" wrote:

If its a standard Triplet the back cell will be a single
lens so there is no need to remove the glass. The front cell
will have two elements. Usually in larger lenses there is a
threaded back cap on the cell but it may have a retaining
ring on the front which is more common for smaller lenses.
If a back cap its easy to remove. The elements are clamped
between concentric edges in the cell so are automatically
centered.
If the cap is too tight for removal with simple finger
grip use one of those rubber jar grippers. It won't mar the
surface. If you grip too tightly it will clamp it and make
it even harder to remove.
I agree with the others about cleaning but if the lens
is oily the standard optical cleaner is pure acetone
followed by dry isopropyl alcohol. Window cleaner like
Windex may streak the lens if not followed by alcohol. The
newer butyl alcohol "streak-free" cleaners are better.
While ammonia is alkaline and strong alkalies can
dissolve some kinds of glass there is no real danger from
the very dilte ammonia in Windex and similar cleaners.
If you use acetone be careful of the edge paint, if any,
and of the paint on the cell because it will dissolve both.
I do not recommend cleaning inside elements when in a
shutter because there is too much danger of getting the
cleaning fluid into the shutter, take the cell out.

--
--
Richard Knoppow
Los Angeles, CA, USA


I'm not absolutely certain about the Geronar formula. It is reported
to be a Tessar.
That said, the rear should be a single piece of glass. But it is not.
If it is a cemented piece, then it is not a true Tessar and the
fogging may be in the cement.
That would be bad.
I've not found the formula out there to describe the lens.
In the mean time I've been searching for a replacement rear cell.


I thought a Tessar had four elements, the rearmost was a cemented doublet.

--
.~. Jean-David Beyer Registered Linux User 85642.
/V\ PGP-Key: 9A2FC99A Registered Machine 241939.
/( )\ Shrewsbury, New Jersey http://counter.li.org
^^-^^ 12:20:01 up 24 days, 20:55, 3 users, load average: 4.74, 4.81, 4.76
  #12  
Old February 13th 11, 06:36 AM posted to rec.photo.equipment.large-format
[email protected]
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Posts: 428
Default Lens Cell Cleaning

On 2/12/2011 12:33 PM, Jean-David Beyer wrote:

Cheesehead wrote:
I'm not absolutely certain about the Geronar formula. It is reported
to be a Tessar.
That said, the rear should be a single piece of glass. But it is not.
If it is a cemented piece, then it is not a true Tessar and the
fogging may be in the cement.
That would be bad.
I've not found the formula out there to describe the lens.
In the mean time I've been searching for a replacement rear cell.


I thought a Tessar had four elements, the rearmost was a cemented doublet.


Lot of confusion in this thread..

A 210mm f6.8 Geronar -IS- a triplet. The rodenstock sales booklet at the
time these were sold stated this.

http://www.bhphotovideo.com/c/produc...nar_Copal.html

A tessar has a cemented doublet but this lens isn't a tessar.

http://en.wikipedia.org/wiki/Tessar

Someone along the way may have swapped out the rear cell from some other
lens into the sample he has or something odd, I have no idea. Maybe he
is confusing a coating problem with fogging inside the cell? I have no
idea on that either.. But the rear cell on a normal 210mm f6.8 geronar
is a single piece of glass.

Stephey




  #13  
Old February 13th 11, 08:22 PM posted to rec.photo.equipment.large-format
Richard Knoppow
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Posts: 752
Default Lens Cell Cleaning

Lots of snipping here................................

"Jean-David Beyer" wrote in message
...
Cheesehead wrote:
Cheesehead wrote:
On Feb 9, 11:41 pm, "Richard Knoppow"
wrote:

I'm not absolutely certain about the Geronar formula. It
is reported
to be a Tessar.
That said, the rear should be a single piece of glass.
But it is not.
If it is a cemented piece, then it is not a true Tessar
and the
fogging may be in the cement.
That would be bad.
I've not found the formula out there to describe the
lens.
In the mean time I've been searching for a replacement
rear cell.


I thought a Tessar had four elements, the rearmost was a
cemented doublet.

--
.~. Jean-David Beyer Registered Linux User
85642.
/V\ PGP-Key: 9A2FC99A Registered Machine
241939.
/( )\ Shrewsbury, New Jersey http://counter.li.org
^^-^^ 12:20:01 up 24 days, 20:55, 3 users, load average:
4.74, 4.81, 4.76


That is correct except that it is possible to have a
"reversed" Tessar with the cemented component in the front.
Also, some Tessar types have the iris in the front air space
instead of the rear even though the cemented component is in
the back.
However, the Geronar is a Cooke Triplet, a
three-element, air-apaced lens with no cemented surfaces.
Its of high quality and such lenses are capable of good
performance at moderate stops.


--
--
Richard Knoppow
Los Angeles, CA, USA



  #14  
Old February 14th 11, 04:39 AM posted to rec.photo.equipment.large-format
[email protected]
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Posts: 428
Default Lens Cell Cleaning

On 2/13/2011 3:22 PM, Richard Knoppow wrote:

However, the Geronar is a Cooke Triplet, a
three-element, air-apaced lens with no cemented surfaces.
Its of high quality and such lenses are capable of good
performance at moderate stops.


From my use, it's a very nice lens given a bad rap mainly because it
was sold at a low price as a "novice lens". Who wants that when you can
buy a pro lens? :P

It's multicoated, comes in a modern, reliable shutter and is
small/lightweight. It actually folds up in my super graphic.

Given most LF lenses are used around f22, the wide open edge performance
isn't an issue for most people. I've actually done some portraits with
mine on 4X5 at f11 and they look great. The only disadvantage I see with
this lens is the smaller image circle compared to the much
Larger/heavier/more expensive plasmat types. If I had to choose this
over some vintage lens that has questionable coatings and flaky/ancient
shutter, I would get this one in a heartbeat.

Stephey


  #15  
Old February 14th 11, 06:04 PM posted to rec.photo.equipment.large-format
[email protected]
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Posts: 428
Default Lens Cell Cleaning

On 2/14/2011 8:37 AM, Cheesehead wrote:


Thanks all.
It looks like my understanding of this lens is in error and that the
rear cell needs to be replaced.
Bummer.



Honestly, you're probably better off just getting another lens. From
what I've seen these don't sell for a lot of money and I'm not sure
where you would even find a replacement rear cell. Maybe find one with a
smashed filter ring or damaged front element (so you can use the one you
have) if you are looking for a cheap way out?

Stephey
  #16  
Old February 14th 11, 07:32 PM posted to rec.photo.equipment.large-format
Thor Lancelot Simon
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Posts: 163
Default Lens Cell Cleaning

In article ,
wrote:

From my use, it's a very nice lens given a bad rap mainly because it
was sold at a low price as a "novice lens". Who wants that when you can
buy a pro lens? :P


Well, at least in the 1990s when the question arose for me, it was more
like "who wants that when you can buy a nice clean used Commercial Ektar"?

Though, actually, knowing what I know now, I'd have gone for a 203/7.7
or a WF Ektar instead, if I were shopping in the Geronar price range
and could only afford one lens.

I suspect most of these that were ever sold were sold with the
Calumet/Cambo kits that bundled them with a moderately priced monorail
camera. I learned with exactly such a kit and it was perfectly good.
But when it came time to buy my own equipment I was strongly advised to
buy a quality used lens instead of a new Geronar, and I think that was
the right advice to give.

--
Thor Lancelot Simon


"We cannot usually in social life pursue a single value or a single moral
aim, untroubled by the need to compromise with others." - H.L.A. Hart
  #17  
Old February 14th 11, 07:58 PM posted to rec.photo.equipment.large-format
David Nebenzahl
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Posts: 1,353
Default Lens Cell Cleaning

On 2/14/2011 5:37 AM Cheesehead spake thus:

Thanks all.
It looks like my understanding of this lens is in error and that the
rear cell needs to be replaced.
Bummer.


Whoa just one second. Before you toss the lens, let me bug you just one
more time.

It seems to have been established that that rear cell is a single
element, not a cemented doublet. In which case any fogging would
actually be on the surfaces(s) of the cell, not internal.

What did you use to clean the lens? Maybe you need to try something
stronger, like acetone, which can dissolve just about any kind of crud.

Might be worthwhile, even if, as others have pointed out, the lens is
not that great: at least you'd have something to shoot with in the meantime.


--
The phrase "jump the shark" itself jumped the shark about a decade ago.

- Usenet
  #18  
Old February 14th 11, 11:57 PM posted to rec.photo.equipment.large-format
[email protected]
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Posts: 428
Default Lens Cell Cleaning

On 2/14/2011 2:32 PM, Thor Lancelot Simon wrote:
In ,
wrote:

From my use, it's a very nice lens given a bad rap mainly because it
was sold at a low price as a "novice lens". Who wants that when you can
buy a pro lens? :P


Well, at least in the 1990s when the question arose for me, it was more
like "who wants that when you can buy a nice clean used Commercial Ektar"?


I actually replaced a "nice clean" commercial ektar of the same length
with this lens and got much better results at my shooting apertures of
f16-f22. Maybe my sample was a bad one but the geronar has much higher
contrast and "snappyness" to the pictures, especially in difficult
lighting. Add to that a much better shutter, I don't think I'd want 50
year old lens with marginal coatings in one of those old supermatic
shutters over this one.

Like I said, this lens gets a bad rap and I suspect most of the people
saying this have never tested or even used one..
  #19  
Old February 15th 11, 01:52 AM posted to rec.photo.equipment.large-format
David Nebenzahl
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Posts: 1,353
Default Lens Cell Cleaning

On 2/14/2011 3:57 PM spake thus:

On 2/14/2011 2:32 PM, Thor Lancelot Simon wrote:

In ,
wrote:

From my use, it's a very nice lens given a bad rap mainly because
it was sold at a low price as a "novice lens". Who wants that
when you can buy a pro lens? :P


Well, at least in the 1990s when the question arose for me, it was
more like "who wants that when you can buy a nice clean used
Commercial Ektar"?


I actually replaced a "nice clean" commercial ektar of the same length
with this lens and got much better results at my shooting apertures of
f16-f22. Maybe my sample was a bad one but the geronar has much higher
contrast and "snappyness" to the pictures, especially in difficult
lighting. Add to that a much better shutter, I don't think I'd want 50
year old lens with marginal coatings in one of those old supermatic
shutters over this one.


What do you mean, "marginal coatings"? Do you think they flake off or
something?

Sorry, but it sounds to me as if you've bought the marketing hype hook,
line and sinker when it comes to "advanced, space-age" coatings. The
only "marginal" here is that modren coatings are marginally better than
the old ones. Hell, even *uncoated* lenses (horrors!) can perform
extremely well (under certain conditions).


--
The phrase "jump the shark" itself jumped the shark about a decade ago.

- Usenet
  #20  
Old February 15th 11, 06:54 PM posted to rec.photo.equipment.large-format
[email protected]
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Posts: 428
Default Lens Cell Cleaning

On 2/14/2011 8:52 PM, David Nebenzahl wrote:
On 2/14/2011 3:57 PM spake thus:

On 2/14/2011 2:32 PM, Thor Lancelot Simon wrote:

In ,
wrote:

From my use, it's a very nice lens given a bad rap mainly because
it was sold at a low price as a "novice lens". Who wants that
when you can buy a pro lens? :P

Well, at least in the 1990s when the question arose for me, it was
more like "who wants that when you can buy a nice clean used
Commercial Ektar"?


I actually replaced a "nice clean" commercial ektar of the same length
with this lens and got much better results at my shooting apertures of
f16-f22. Maybe my sample was a bad one but the geronar has much higher
contrast and "snappyness" to the pictures, especially in difficult
lighting. Add to that a much better shutter, I don't think I'd want 50
year old lens with marginal coatings in one of those old supermatic
shutters over this one.


What do you mean, "marginal coatings"? Do you think they flake off or
something?

Sorry, but it sounds to me as if you've bought the marketing hype hook,
line and sinker when it comes to "advanced, space-age" coatings. The
only "marginal" here is that modren coatings are marginally better than
the old ones. Hell, even *uncoated* lenses (horrors!) can perform
extremely well (under certain conditions).




I guess you missed the "difficult lighting? And yes those early coatings
were good, just not as good as later ones. And yes I do use uncoated
lenses too so understand your point here. In tough lighting the ektar
created low contrast chromes.

I didn't make this judgment based on marketing. I wouldn't have bought
a geronar at all if I wasn't having issues with the commercial ektar of
the same length. I have a 135mm WF ektar and the images it makes are
nice and crisp compared to the ones I was getting with the comm ektar,
hence I looked for a replacement. I have never considered replacing the
135mm WF ektar, it works just fine so don't thing older coating are rubbish.

Sorry if posting that -in my experience- this "novice" lens performs
much better that my old commercial ektar did- rocks the boat of people
who are sold on those old lenses are somehow some sort of religious
experience. I could see nothing wrong looking at the commercial ektar,
maybe it was a bad one? I can only base this on my experience. It was a
-sharp- lens but didn't have the contrast/snappyness this geronar has.
So to say "-Blank- old lens is a better choice" didn't work out for me.

Stephey
 




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